lineageos-ota-server/processFiles.go

package main

import (
	"archive/zip"
	"bufio"
	"crypto/sha1"
	"crypto/sha256"
	"fmt"
	"io"
	"io/fs"
	"log"
	"os"
	"strconv"
	"strings"
)

type ZipMetadata struct {
	Timestamp        int
	SDKLevel         int
	PatchLevel       string
	OTAPropertyFiles string
}

// Searches the build toolchain output directory for new LineageOS builds.
// Any new builds are moved into the public http server directory.
// Returns true if new builds were moved
func moveBuildArtifacts() bool {

	f, err := os.Open(buildOutDirectory)
	if err != nil {
		log.Printf("failed to open ROM directory: %v", err)
		return false
	}
	defer f.Close()
	files, err := f.ReadDir(0)
	if err != nil {
		log.Printf("failed to read files in directory: %v", err)
		return false
	}

	var newROMs bool

	for _, v := range files {
		if isLineageROM, _ := parseROMFileName(v); !isLineageROM { // skip files that aren't LineageOS ROMs
			continue
		}

		newROMs = true
		log.Printf("new build found - moving file %s", v.Name())
		romCache.Lock() // RW lock to prevent multiple concurrent goroutines moving the same file
		err := copyThenDeleteFile(fmt.Sprintf("%s/%s", buildOutDirectory, v.Name()), fmt.Sprintf("%s/%s", romDirectory, v.Name()))
		romCache.Unlock()
		if err != nil {
			log.Printf("failed to move file '%s' from out to rom directory: %v", v.Name(), err)
			continue
		}
	}

	return newROMs
}

// Returns a sha256 hash of a file located at the path provided
func hashFile(filename string) (string, error) {
	_, sha256Val, err := hashFileSha1AndSha256(filename)
	return sha256Val, err
}

// Returns sha1 and sha256 hashes of a file located at the path provided
func hashFileSha1AndSha256(filename string) (string, string, error) {
	f, err := os.Open(filename)
	if err != nil {
		return "", "", fmt.Errorf("failed to open file '%s': %v", filename, err)
	}
	defer f.Close()

	h1 := sha1.New()
	h256 := sha256.New()

	buf := make([]byte, 32768)
	for {
		n, err := f.Read(buf)
		if n > 0 {
			h1.Write(buf[:n])
			h256.Write(buf[:n])
		}
		if err == io.EOF {
			break
		}
		if err != nil {
			return "", "", fmt.Errorf("failed to read file '%s': %v", filename, err)
		}
	}

	return fmt.Sprintf("%x", h1.Sum(nil)), fmt.Sprintf("%x", h256.Sum(nil)), nil
}

// Reads metadata from META-INF/com/android/metadata inside the zip file
func readZipMetadata(zipPath string) (ZipMetadata, error) {
	var meta ZipMetadata

	r, err := zip.OpenReader(zipPath)
	if err != nil {
		return meta, err
	}
	defer r.Close()

	for _, f := range r.File {
		if f.Name == "META-INF/com/android/metadata" {
			rc, err := f.Open()
			if err != nil {
				return meta, err
			}
			defer rc.Close()

			scanner := bufio.NewScanner(rc)
			for scanner.Scan() {
				line := scanner.Text()
				parts := strings.SplitN(line, "=", 2)
				if len(parts) == 2 {
					key := strings.TrimSpace(parts[0])
					val := strings.TrimSpace(parts[1])
					switch key {
					case "post-timestamp":
						t, _ := strconv.Atoi(val)
						meta.Timestamp = t
					case "post-sdk-level":
						s, _ := strconv.Atoi(val)
						meta.SDKLevel = s
					case "security-patch-level":
						meta.PatchLevel = val
					case "ota-property-files":
						meta.OTAPropertyFiles = val
					}
				}
			}
			return meta, scanner.Err()
		}
	}

	return meta, fmt.Errorf("metadata file not found in zip")
}

// false if a file is not a LineageOS ROM .zip file
// no formal validation is performed - only file naming convention is checked
// also returns a lineage ROM's filename sliced and delimited by -'s
// Example filename: lineage-20.0-20230604-UNOFFICIAL-sunfish.zip
func parseROMFileName(v fs.DirEntry) (bool, []string) {

	// skip directories, non .zip files and files that don't begin with lineage-
	if v.Type().IsDir() || !strings.HasSuffix(v.Name(), ".zip") || !strings.HasPrefix(v.Name(), "lineage-") {
		return false, nil
	}

	splitName := strings.Split(v.Name(), "-")
	// expect 5 dashes
	return len(splitName) == 5, splitName
}

// A custom "move file" function because in docker container the mounted folders are different overlay filesystems
// Instead of os.Rename, we must copy and delete
func copyThenDeleteFile(src, dst string) error {
	sourceFileStat, err := os.Stat(src)
	if err != nil {
		return err
	}

	if !sourceFileStat.Mode().IsRegular() {
		return fmt.Errorf("%s is not a regular file", src)
	}

	source, err := os.Open(src)
	if err != nil {
		return err
	}
	defer source.Close()

	destination, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer destination.Close()
	_, err = io.Copy(destination, source)
	if err != nil {
		return fmt.Errorf("failed to copy file: %v", err)
	}

	err = os.Remove(src)
	if err != nil {
		return fmt.Errorf("failed to delete source file after copy: %v", err)
	}

	return nil
}